Allergic diseases are still a major health problem due to their high incidence (20 to 30% of the population) and to the lack of curative treatment. Usually the therapy is restricted to the use of antihistamines or to more or less effective immunization procedures. The classical antiallergic drugs have certain disadvantages, especially since they cause various side effects in the treated patient. The immunization procedure is limited to one or two allergens whereas most of the patients are sensitive to a large number of allergens. In addition, hyposensitization treatment is neither curative nor protective.
The vast majority of allergic diseases are mediated by immunoglobulin E (IgE) antibodies directed against a myriad of airborne allergens, e.g. pollens, animal danders or house dust mite, etc., food antigens, pharmacological agents, e.g. penicillins, or hymenoptera venom. The mechanisms regulating the production of IgE have been extensively investigated in laboratory animals [K. Ishizaka, Ann. Rev. Immunol. 2, 159 (1984)]. These studies have clearly indicated the existence of non antigen specific but IgE isotype specific mechanisms controlling the production of IgE in animal models. The effector molecules of these regulatory mechanisms were named IgE-binding factors (IgE-BFs) owing to their affinity for IgE. IgE-BFs may be divided into IgE-suppressive factors (IgE-SFs) and IgE-potentiating factors (IgE-PFs): These molecules differ only by their carbohydrate content. IgE-SFs are not glycosylated or less glycosylated than the corresponding IgE-PFs. The actual production of IgE in animal models is determined by the ratio between these two kinds of IgE-BFs.
The same cells are capable of secreting either IgE-SFs or IgE-PFs depending on the influence of either glycosylation inhibiting or enhancing factors which are secreted by distinct regulatory T lymphocyte subpopulations.
M. Sarfati et al. [Immunology 53, 197, 207, 783 (1984)] have documented the existence of human B cell lines secreting IgE-BFs endowed with the same biological activities as those described in rodents. Other investigators have described the production of IgE-BFs by human T cells [T.F. Huff and K. Ishizaka, Proc. Natl. Acad.Sci. (USA) 81, 1514 (1984)]and rat/mouse T-cell hybridoma [European Patent Application 155 192]. The relationships between IgE-BFs of T cell origin and those of B cell origin are not known. The present invention now provides IgE-BFs from human B cells in highly purified form.
It is already known that breast-feeding may alter the immune reactivity of the newborn. Recent prospective studies further indicated that exclusive breast-feeding protects the high risk infants against allergic disease. Multiple mechanisms are invoked to explain these observations: (i) A reduced exposure to foreign food antigens, (ii) the protection by milk IgA blocking antibodies specific to various alimentary antigens and to other environmental antigens, (iii) the protection against common viral diseases known to trigger the onset of allergic diseases, and finally (iv) the presence in human milk of immunoregulatory factors capable of modulating the immature immune system of the neonate [S. S. Crago and J. Mestecky, Surv.Immunol.Res. 2, 164 (1983)]. The well documented observation on the immunoreactivity of breast-fed newborns might be explained by the presence in human colostrum of specific antibodies or idiotypes, immunoregulatory factors, or regulatory lymphocytes. Hence, it is suggested that breast-feeding may protect newborns by providing them with either IgE-suppressive factors or with other molecules (such as glycosylation inhibiting factor) or cells capable of interfering with the infants lymphocytes involved in the regulation of IgE antibody production [S. A. Roberts and M. W. Turner, Immunology 48, 195 (1983); E. Jarrett and E. Hall, Nature 280, 145 (1979)].
So far IgE-BFs with IgE-SF activity have not been identified in human colostrum, and the isolation thereof is nowhere described. Surprisingly, such IgE-BFs have now been isolated in highly purified form.
IgE plays an important role in the development of allergic diseases. Purified IgE-binding factors are therefore important for the diagnosis and therapy of allergic diseases and immune regulation diseases connected therewith. In particular IgE-BFs with IgE-suppressive activity might be useful in the treatment of allergic diseases, whereas IgE-BFs with IgE-potentiating activity might increase resistance to infections, for example resistance to parasitic infections.
The known assays for the detection of IgE-BFs are based on a rosette inhibition test wherein RPMI 8866 cells from a lymphoblastoid B cell line expressing receptors for IgE (FctR) are rosetted with IgE-coated bovine erythrocytes. If the latter are first preincubated with IgE-BFs, they are no longer able to bind to RPMI 8866 cells and the proportion of cells forming rosettes is reduced accordingly. This assay is not quantitative, it is technically delicate due to the variability in the coupling of IgE to bovine erythrocytes and it is cumbersome, because rosettes must be examined under the microscope, cell lines must be permanently available, IgE-coated erythrocytes must be prepared regularly, etc., so that only a small number of tests (20-40) can be reasonably performed by one person in one day. Hence, it would be most desirable to dispose of a quantitative, easy to perform assay that could be applied on a large number of samples, e.g. several hundreds per day. Such an assay would not only facilitate the research on the physiopathology of IgE-BFs but it might also be employed to monitor the purification of IgE-BFs from various biological fluids, such as culture supernatants from cell lines secreting IgE-BFs. Furthermore, it could be employed to detect and quantify IgE-BFs in the serum for diagnostic purposes.
The present invention provides a solution to the aforementioned problems through the preparation of monoclonal antibodies to lymphocyte Fc.sub..epsilon. R crossreacting with IgE-BFs. At the same time these monoclonal antibodies allow an efficient purification of IgE-BFs by affinity chromatography. The known purification of IgE-BFs by affinity chromatography on IgE-coupled solid phase has been entailed with a low yield compromising further studies on the purified factor due to the low affinity of IgE to IgE-BFs.